Lightning-arrester.



PATENTED AUG. 25, 1908.

K. KU HLMANN. LIGHTNING ARRESTER."

APPLICATION FILED MAR.15, 1907.

J IZLNTUH W ATTX ' UNITED srarns ,ATENT FFIGE;

KARL KUHLMANN, OF BERLIN, PANKOW, GERMANY, ASSIGNOR TO GENERAL ELECTRICCOMPANY, A CORPORATION OF NEW YORK.

LIGHTNING-ABRESTER.

Specification of Letters Patent.

PatentedAug. 25, ieoe.

Application filed March 15, 1907. Serial No. 362,480.

in series with resistances andare arranged to form dischargepathsbetween the line conductors and between conductors and ground.

Various groupings of the resistances and spark gaps have been proposedto decrease the total number of resistance units, but too littleattention has heretofo'rebeen aid to the point of creating excesspotentia paths according to the frequency of the excess potentials. Thenumber of oscillations of an electrical discharge is of essentialinfluence on the path selected for its passage. Thus, for example, ahigh frequency discharge will choose a path through spark gaps or 0011-densers in preference to that through ohmic resistance,since thelattercannot be so formed as to offer an entirely inductionless path tovery rapidly alternating current.

The arrangement described below embodies the principles above set forth.

One novelty of the new arrangement con-.

sists in the s ecial provision of paths for the rapidly oscil atingpulsations.

In the accompanying drawing, Figure 1 is a diagrammatic representationof an electrical system protected according to my invention;

Fig. 2 shows a system with reactance devices in series with the lineconductors; Fig. 3 shows how the system of Fig. 2 can'be simplified andimproved; and Fig. 4 illustrates my invention as applied to a singlephase circuit. 7

The protective means illustrated in Fig. 1 consists of a plurality ofresistances and a plurality of safety devices, so grouped that aplurality of paths for current discharge are ()llllOtl, the paths beingradically different in reactive effect and therefore having a selectiveaction on discharges of different frequencies. The safety devices abovementioned may be either spark gap or condensers. The line conductors 1,2 and 3 of the three-phase system are connected respectively with theresistances 4:, 5 and 6, and these are connected to ground throughsafety devices 7, 8 and 9.

. Each of these resistances is also connected in to another lineconductor through safety devices and small resistances. Thus, resistance4 is connected in to line conductor 2 through spark gap 10 and smallresistance 11, and resistances 5 and 6 are similarly connected inthrough spark gaps 12 and 13, and resistances 14 and 15. The exactarrangement will be clearly understood by reference to Fig. 1 of theaccompanying drawing. In this case, the discharge passing from a 'lineconductor to earth, passes through only a singleresistance, such as 4,5, or 6, but a discharge passed between two line conductors passessuccessively through a large resistance, as 4, and a small resistance,as 1].; there lies therefore,

in the path of thegreater potential, also the greater resistance. Thepath above outlined is that for a discharge of relatively low frequency,and in case the charge on conductor 1 is of high frequency it passes toground through small resistance 15 and safety devices 13 and 9 It willbe understood that each' line conductor is provided with two dischargepaths to ground, one having a large resistance and a single safetydevice, and the other having a small resistance and aplurality of safetydevices. "It will be also understood that each conductor has two pathsto any other con ductor, one of relatively high resistance and suitablefor low frequency currents, and the other containing less resistance andbetter adapted for very high frequency currents. It is advantageous toemploy the above described arrangement in conjunction with the chokingcoils which are often used as lightning protectors. If, for example,machines which are connected to an opendead system are .to be protectedagainst excess 9 potentials by using choking coils between conductor andearth, or-between the individual conductors, three spark sections foreach individual lead may be employed in series with three separateresistances. According to this scheme, athree-phase circuit requiresnine sparking sections in all and nine resistances, as illustrateddiagrammatically in Fig. 2. According to this arrangement, the groundedsparking sections 16, 17 and 18 are branched off before their respectivechoking coils 1 9, 20 and 21, and similar grounded sections 22 23 and 24are branched oil behind these choking coils.

In the arrangement shown in Fig. 3 the choke coil for any conductor isconnected between the two discharge paths leading from that conductor tothe other. It is therefore no longer necessary to include excesspotential safety devices in these con nected paths. The choke coils 25,26 and 27 serve to prevent an excessive flow of line current in case ofa high potential .discharge through any of the large resistances 28, 29and 30', or through the low impedance paths including resistances 31, 32and 33 and spark gaps 34, 35 and 36.

Fig. 4 shows the same general idea applied to a single phase system.Reactances 37 and 38 are included in the line conductors, the highresistances 39 and 0 are connected to the line conductors on one'side ofthe reactance coils, and resistances 41 and 42 of lower magnitude areconnected on the opposite sides of the reactance coils. The reactancesmay be considered as connected in series with the discharge'paths andserve to choke down any abnormal flow of line current.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is,

1. The combination with a plurality of .l ine conductors ofan electricalsystem, of a high resistance and also a safety device and a lowresistance forming a discharge path from one line conductor to another,and a safety device of low reactance connected between ground and thejunction point of said higl resistance with its safety device. I

2. The combination with line conductors of an electrical system, of areactance in series with each line conductor, 'a discharge path forabnormal charges, said path including a resistance and a safety device,said path connecting opposite ends of two-of said line .reactances torender thereactances effective for cutting down the 'fi'ow of linecurrent through said discharge path.

3. .The combination with a plurality of conductors of an electricalsystem, of a react-- ance in series with each of said. conductors, adischarge path connecting opposite sides of the reactances in two ofsaid conductors, said path including a high resistance and also asafetydevice and a low resistance, and a safety device between groundand the junction point of said resistance with its safety device. a

'4. The combination with line conductors of a three-phase electricalsystem, of a discharge path between each conductor and every otherconductor, each of said paths including a large resistance and also asafety device and asinall resistance, and a ground connection'for thejunction point of each high resistance with its corresponding safetydevice, said ground connections being of low reactance and including asafety device.

5. The combination with line conductors, of an electrical system, ofreactance coils in Said line conductors, a discharge path from one lineconductor to another for transmitting charges of relatively lowfrequency, said path including a large resistance and connectingopposite ends of two of said line reactances, and a path to ground forone of said line conductors, said path including a portion of the pathbetween two conductors and having much. less reactance than that of saidlarge resistance,

In witness whereof I have hereunto set my hand this 23rd day ofFebruary, 1907.

KARL KUHLMANN. Witnesses:

JULrUs RUMLAND, -KARL MIOKEBEN.

